The present invention relates generally to medical temperature probes, and more particularly to a temperature probe comprising a spring-loaded shaft for maintaining a constant force between the shaft and a temporary, disposable probe cover, and a mechanism to eject the probe cover from the probe.
Medical thermometers are useful in the diagnosis and treatment of many diseases. It is common practice in the medical arts, as in hospitals and in doctors"" offices, to measure the body temperature of a patient by means of a glass bulb thermometer incorporating a heat responsive mercury column that expands and contracts adjacent a calibrated temperature scale. It is also known to use electronic thermometers that operate to sense the patient""s temperature for a short period of time and then extrapolate to predict the actual patient temperature. This latter thermometer results in the determination of a patient""s temperature in a much shorter time period than with mercury glass bulb thermometers.
While these thermometers have been used for many years and have been found to provide useful results in diagnosing and treating patients, some of those who use them desire a thermometer that determines a patient""s temperature more rapidly. For example, a mercury thermometer typically takes at least five minutes or more to determine a patient""s temperature. An electronic predictive thermometer can take one or more minutes in its predictive mode and five or more minutes in its monitoring or direct reading mode. Electronic predictive thermometers have become popular because in their predictive mode, the time for taking the temperature is much less than the mercury thermometer. For busy nursing staffs, time is of the essence. Taking a temperature in one minute is much more desirable than taking a temperature in five minutes. More patients can be served with the faster thermometer and the nursing staff can be more productive.
Additionally, the more time that a probe must be in a patient""s mouth to make a temperature determination, the more likely it is that the probe will not remain in the correct location. This is particularly true with younger patients who tend to be impatient. For patients who cannot be relied upon (by virtue of age or infirmity for example) to properly retain the thermometer for the necessary period of insertion in the body, the physical presence of medical personnel during a relatively long measurement cycle is necessary. Taking a temperature of younger patients in one minute is immensely more desirable than taking the temperature in five minutes. Thus, the predictive electronic thermometer has substantially advanced the art of temperature determination.
In addition to the above, rapid reuse on other patients is also a goal. However, with reuse, precaution must be taken to avoid the possibility of cross contamination between patients. Consequently, protective covers have been designed for use with the probes of thermometers. The protective cover is designed to completely envelop the portion of the thermometer that comes into contact with the patient. Because the protective cover may then be removed and discarded after use of the thermometer, and because the protective cover has protected the thermometer from contact with the patient, the thermometer may be immediately reused by simply applying another protective cover.
Protective probe covers have been available for predictive electronic thermometers for many years making the thermometer rapidly reusable when properly used with such covers. However, a protective cover adds material between the temperature sensor in the probe of the thermometer and the heat source; i.e., the patient. Additional material between the patient and the sensor can slow down the process of determining the patient""s temperature as heat from the patient must first pass through the probe cover before it reaches the sensor. Gains made in permitting immediate reuse of thermometers due to the use of a disposable probe cover may thus be offset by the increasing length of time it takes to obtain a reading, caused by that same probe cover.
In addition, given that each probe cover is used only once and then discarded, it is desirable that such probe covers be as inexpensive as possible. They should be efficiently produced from readily available, inexpensive materials utilizing common manufacturing techniques. Thus, materials offering good heat transfer characteristics and that are easily injection molded, such as thermoplastics, are desired in fabricating probe covers.
One factor in obtaining a temperature measurement in as short a time as possible is to improve the heat transfer characteristics between the probe and the probe cover. A consideration in the heat transfer characteristics of a probe cover is the contact the probe cover makes with the probe tip in which the temperature sensor is located. As is well known to those skilled in the art, air located between a probe cover and the sensor in the probe tip will act as an insulator and will slow down the transfer of patient heat to the sensor. It will then take longer to obtain a measurement of the patient""s temperature. Poor contact between the probe cover and the probe will also slow down the measurement process in that heat from the patient will take longer to reach the sensor in the probe tip. Consequently, most probe and probe cover systems are designed and configured to achieve good contact between the tip of the probe, where the temperature sensor is located, and the inside surface of the probe cover so that patient heat is transferred more quickly to the temperature sensor.
Probes used with probe covers by necessity have a cover retention mechanism. A number of prior art devices relied upon the interference fit between the probe shaft distal tip and the probe cover for retaining the cover onto the probe. It is desirable in some cases where a precise interface between the probe tip and the probe cover is required to retain the probe cover onto the probe by other means.
Another design for cover retention is a split ring. In use, the probe cover is mounted over the probe shaft and pressed down over the split ring, forcing the ring to contract and thus allow the probe cover to slip over its outer periphery. The natural tendency of the ring is to return to its original shape thereby applying outward force against the probe cover, and thus retaining the cover in position over the probe. While this design has been accepted and has provided improvement to the art, in some cases a less complex design would be desired. The split ring is an extra part that must be manufactured and assembled with the probe, and thus adds to the overall complexity and cost of the probe.
Thermometers having a probe configured for receiving disposable probe covers have also been used for many years with ejection systems. In one particular design, an ejection mechanism is used to detach the probe cover from the probe after use so that the contaminated probe cover can be directly discarded without the operator having to touch it. In the typical case, the probe is held over a waste receptacle, the ejection button is pressed which detaches the probe cover from the probe and the probe cover falls into the waste receptacle. Different types of ejection mechanisms exist.
In one ejection mechanism, the probe shaft of the thermometer is coupled directly to the ejection mechanism. The probe cover is mounted over the probe and is retained in position by a retention device located at the distal end of a handle forming part of the probe. For ejection, the ejection button is pressed which causes the probe shaft to extend farther out of the probe handle pushing the probe cover also in a distal direction away from the retention device and dislodging the probe cover from a retention device. The probe cover then falls off the probe. Some improvement on this device is desired as the ejection button provides a natural resting place for the user""s thumb, and in some cases, the user may inadvertently and prematurely press the ejection button before the temperature measurement has been completed. This inadvertent pressing may move the probe cover in relation to the probe and change the quality of contact of the probe cover with the probe tip. As discussed above, the heat transfer characteristics between the probe cover and the probe tip can affect the speed with which the thermometer can measure the patient""s temperature. Should the quality of contact be changed, the patient""s temperature measurement may be slowed down. Thus, it would be desirable to decouple the ejection button from contact with the probe tip and probe cover.
In a worse case, the inadvertent press of the ejection button may cause the probe cover to come completely off the probe before or during the measurement procedure. The measurement may then have to be repeated with a new probe cover thus wasting time of the patient and nurse, and wasting a probe cover.
In another approach, the probe is fixed to the handle and has a fixed length. Ejection of the probe cover is effected by a mechanism that presses against the proximal edge of the probe cover. Probe covers used with this type of probe must be manufactured in a relatively specific range of lengths, because a cover that is too short will not engage the retainer device and a cover that is too long will not make proper, or any, contact with the probe tip and thus not provide the speed of measurement desired. Such tight manufacturing tolerances typically require sophisticated equipment and additional processing and quality control steps, and thus usually lead to increased production costs.
Hence those skilled in the art have recognized a need for a temperature probe usable with probe covers that can be inexpensively produced from readily available, inexpensive materials utilizing common manufacturing techniques. In addition, it has been recognized by those skilled in the art that a need exists for an ejection mechanism that is decoupled from the probe tip/probe cover contact so as to not affect such contact until actual disposal of the probe cover is desired. The invention fulfills these needs and others.
Briefly and in general terms, the present invention is directed to a temperature probe for use with a probe cover having a closed distal end and an open proximal end, comprising a shaft having a distal end for receipt into the probe cover through the probe cover open proximal end and a proximal section, a retention device located at the proximal section of the shaft configured to engage the proximal end of the probe cover and retain it in position on the shaft, a handle disposed at the proximal section of the shaft such that the shaft extends into the handle for axial movement therein between a fully retracted position and a fully extended position, the handle having a proximal end, a biasing member disposed within the handle and urging the shaft to the extended position, the biasing member providing less force to move the shaft into the extended position than the force that the retention device is providing to retain the probe cover on the shaft, an ejector control having a distal end slidably received in the proximal end of the handle and having a proximal end for use in receiving force that urges the ejector control into the handle, and an ejector member connected with the ejector control and extending longitudinally through the handle to exit the handle adjacent the shaft and contact the probe cover at its proximal end whereby moving the ejector control in a predetermined direction will cause the ejector member to press against the proximal end of the probe cover and displace it from contact with the retention device, whereby the probe cover may be removed from contact with the probe.
In further detailed aspects, the retention device comprises a raised lip formed in a shape different that than of the proximal end of the probe cover such that when mounting the probe cover onto the retention device, the proximal end of the probe cover is forced to conform to the shape of the lip. The circumferential size of the lip is approximately equal to the circumferential size of the probe cover whereby the probe cover is held onto the lip by the forces exerted against the lip by the probe cover as a result of the different shape the probe cover has been forced into by the lip. The lip is generally oval in shape.
In other aspects, the ejector member comprises two ejector devices and the oval shape of the lip includes two flat portions diametrically located at which the ejector devices exit the handle to contact and eject the probe cover. The retention device comprises at least one barb protruding radially outwardly adjacent the distal end of the handle which secures the probe cover thereto. The biasing member comprises a spring which is placed under compression when a probe cover is mounted to the probe, whereby the spring continually urges the probe against the probe cover. The biasing member is selected such that the force it exerts against the shaft is within a selected range. In another aspect, the range of force exerted by the biasing member is between one half pound and one pound.
In yet further aspects, the ejector member comprises two ejection devices located diametrically opposite each other about the shaft. The ejector devices comprise pins located in the handle so as when the ejection control is activated, the ejector devices contact the proximal end of the probe cover and move it in a distal direction off the retention device.
In other detailed aspects, the length of the probe is selected to be longer than the probe cover such that when the probe cover is properly mounted on the probe the probe shaft is retracted. The ejector control comprises an end surface formed with an aperture therein for slidably accepting an electrical conductor therethrough. The end surface of the ejector control is curved outwardly from the aperture for controlling the maximum degree of curvature to which the conductor is subjected as it exits the probe. The end surface has a curved funnel-shaped surface to control the maximum amount of curvature of a cable extending through the opening.
In yet other detailed aspects, the retention device is formed as part of the handle and comprises a lip protruding radially outwardly from the distal end of the handle and having a diameter selected to be larger than the inside diameter of the probe cover thereby securing the probe cover thereupon.
In yet another aspect, provided is a temperature probe for use with a probe cover having a closed distal end and an open proximal end, comprising a handle having a proximal end and a distal end, a probe shaft having a proximal section mounted to the handle distal end and a distal end for receipt into the probe cover through the probe cover open proximal end, a retention device located at the distal end of the handle configured to engage the proximal end of the probe cover and retain it in position on the shaft, and an ejector member located at the handle to exit the handle adjacent the probe shaft and contact the probe cover at its proximal end whereby moving the ejector member in a distal direction will cause the ejector member to press against the proximal end of the probe cover and displace it from contact with the retention device.
These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings, which illustrate by way of example the features of the invention.